Non-enveloped gel prosthesis

ABSTRACT

An unconstrained cohesive gel prosthesis is disclosed for implantation in a human body. The prosthesis consist essentially of an unconstrained, pressure-disbursing, cohesive, homogenous gel which can be stretched substantially more then 21% of its length without the appearance of stress cracks.

This application is a continuation in part of U.S. application Ser. No.781,305 filed Sept. 27, 1985 now U.S. Pat. No. 4,740,208, which is acontinuation of application Ser. No. 613,894 filed May 24, 1984, nowabandoned, which is a continuation of application Ser. No. 209,021 filedNov. 21, 1980, now U.S. Pat. No. 4,470,160, the priorities of which areclaimed.

BACKGROUND OF THE INVENTION

This invention relates to gel elastomer implantable prostheses and, moreparticularly, relates to subcutaneous gel elastomer implants.

Early on, silicone gel used for cosmetic purposes was in the form ofliquids which were injected subcutaneously. However, serious problemsdeveloped because of the migration of the silicone gel into surroundingtissue causing granulomas. These problems became so serious that use ofliquid gels was all but stopped. To solve the problem of the migrationof the liquid gel, several solutions have been proposed and adopted.Among these was the encapsulation of the silicone gel in one or moreartificial plastic or silicone envelopes and implanting this prosthesissubcutaneously. This, however, created altogether new problems.

When such implants are used, for example, in mammaplasty procedures, anatural tissue capsule forms around the implant. Since the advent of theenvelope-encased implant, doctors have been fighting the problemsfollowing these augmentation mammaplasty procedures, particularlybecause of the firmness caused by the contracture of the natural tissuecapsule which is formed and which tightens around the encased implant.The answer to this problem was thought to be an open or closedcapsulotomy, leaving the implant intact. The closed capsulotomyprocedure consisted of crushing (i.e. breaking up) the natural tissuecapsule by manipulation of the tissue or breast. Alternatively, an openor surgical capsulotomy was sometimes performed. However, neither ofthese procedures have been effective because they do not get rid of theoffending foreign body. That is, the body starts the process of formingthe natural tissue capsule over again, resulting in contracturesproducing excessive firmness and deformity and, in some cases, pullingand painful sensations to the patient with distorted and extremely firmresults.

One logical way to solve the problem would be to place the implant inthe tissue with the envelope and allow it to remain until the naturaltissue capsule is formed which usually will occur within approximatelysix weeks. The silicone envelope could then be removed, allowing thenatural tissue capsule to contain the silicone gel without allowing itsmigration into surrounding tissues. However, of course, this requires asecond procedure and there is no guarantee that some migration willstill not occur.

Thus, it was determined that the solution to the overall problem was toprovide an implant which eliminated the offending foreign body (i.e.,the silicone envelope) and provide an implant which would eliminate thepossibility of migration.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a silicone gelelastomer implantable prosthesis which will maintain the naturalsoftness of the surrounding tissue after implantation.

In order to solve the problem of maintaining the natural softness of thesurrounding tissue, a silicone gel elastomer implantable prosthesis,having a cohesive homogeneous construction with or without minimalmembrane coating, is the most important feature of the inventionproposed herein. The implantable prosthesis disclosed and describedherein, is particularly suitable for use in mammaplasty providingsofter, natural breasts for women for use in breast augmentation. Theprinciples of the invention involve the use of a cast gel implantableprosthesis which may have a minimal membrane coating, or in thealternative, utilizing an absorable shell which would be completelydissolved after approximately six weeks or so. Another alternative wouldbe to provide an easily removable artifical envelope of siliconematerial which could be removed as soon as the natural tissue capsule isformed. In each case, however, the silicone gel implant would be formedof a cohesive gel material, having a predetermined consistency.

Thus, adoption of the cast gel implantable prosthesis of the presentinvention would result in the removal of the offending foreign body;that is, the artificial envelope which continually causes problems. Thiswould eliminate any further need for manipulating, crushing, squeezingor uncomfortable maneuvers to the breast area to break up the naturaltissue capsules. These procedures are destroying the wrong envelope andonly provide a temporary solution. By forming the silicone gel implantof a cohesive material having a predetermined consistency, the implantwould be contained by the natural tissue capsule and will not migrateinto any surrounding tissues, and will, at the same time, maintain thesoft, natural feeling of the surrounding tissue.

The manufacturer of the silicone implants and, particularly, those foruse in mammaplasty, would comprise mixing a suitable feeling gel havinga predetermined consistency and forming it into an implant or prosthesisin a mold. The mold would be designed for various shapes and sizesproducing products which would vary in size and shape, depending uponthe need. After vulcanizing the prosthesis in the mold, it will beremoved and, in some cases, might be treated with a silicone fluid orelastomer to reduce tackiness. The prosthesis is then ready forimplantation as is, or may be covered with an easily removable temporaryenvelope. If an artificial silicone envelope is used, it of course wouldhave to be removed after a predetermined period of time. Possibly, adissolvable or absorbable type envelope, such as one formed fromcollagen or various other types of materials may be used. Alternatively,after the mold process, appropriate coating of the implant could produceor provide an extremely thin, integral layer which would also maintainthe natural feeling and not present any type of foreign body producing adouble envelope condition, as with previous implants.

Also included in the invention are the incorporation, if desired, oforientation marks in the prosthesis, as well as integrally incorporatingfixation patches where needed, in order to position and hold the implantto surrounding tissue. The fixation material, or patches, could beinserted in the gel material prior to vulcanizing of the gel compound.The gel compound is formed and produced to provide a consistency orcross-link density which may be varied to yield different textures of"feeling". The cohesiveness or cross-link density (sometimes calledconsistency) preferred would be in the range of approximately 0.1 mm-30mm, as measured with a penetrometer. The important, unique feature isthe elimination of any type of permanent envelope forming an offendingforeign body from the use in an implant and, particularly, for use inmammaplasty.

The object of the present invention is to provide a cast gel implantableprosthesis which produces the natural feeling of the surrounding tissue.

Another object of the present invention is to provide a cast gelimplantable prosthesis without any artifical envelope.

Yet another object of the present invention is to provide a cast gelimplantable prosthesis having a predetermined cohesiveness forsubcutaneous implantation.

Another object of the present invention is to provide a cast gelimplantable prosthesis having integrally incorporated fixation patches.

These and other objects of the invention become obvious from thefollowing detailed description of the invention when considered inconnection with the accompanying drawings wherein like reference numbersidentify like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of one prosthesis formed according to theinvention;

FIG. 2 is a side view of the prosthesis illustrated in FIG. 1;

FIG. 3 is a view illustrating the use of the prosthesis shown in FIG. 1for augmentation mammaplasty operation;

FIG. 4 is a sectional view illustrating the placement of the prosthesisin an augmentation mammaplasty operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A cast gel implantable prosthesis which may be coated is illustrated at10 in FIG. 1 and is comprised of 100% pure silicone gel formed to have apredetermined cohesiveness or cross-link density, sometimes calledconsistency. Perferably, the gel is sufficiently cohesive to withstandstretching to at least 21% of its normal dimension without theappearance of stress cracks. The particular implant shown is foraugmentation mammaplasty which is the principal use of such prosthesis,but could be formed in any size, shape for any type of surgicalimplantation. In the particular implant shown, it is generally circularin shape and has a substantially ovular cross-sectional shape. Theprosthesis is manufactured by preparing a compound and mix of a suitableconsistency with the mold of which there may be various shapes and sizesto produce products which may be varied according to need. The gelcompound is then vulcanized in the mold and removed. The surface of theprosthesis then may be treated with a suitable silicone fluid orelastomer to reduce tackiness. In addition, the implant may have a verythin coating to provide an integral silicone layer or skin, if desired.

Additionally, during the manufacture of the case gel implantableprosthesis, it may also be provided with a fixation patch as indicatedat 18 or at other areas, and a suitable silicone coating or envelope 20.The envelope 20 can be formed of a dissolvable, absorbable material suchas gel foam, treated with a topical thrombin to minimize bleeding afterinsertion, Surgicel (oxidized regenerated cellulose), Dexon(polyglycolic acid), Vicryl (polyglacatin) or any other suitable type ofabsorbable material. The fixation patches could be also comprised of asilicone or Dacron material and are formed integrally with theprosthesis during the molding process. The fixation patch or patchesillustrated at or around 18 are for the purpose of holding the implantin position by fibrosis into the fixation patch or patches by locallizedtissue.

To illustrate the unique function and method of this invention, FIGS. 3and 4 show the prosthesis illustrated in FIGS. 1 and 2 used in anaugmentation mammaplasty. The augmentation mammaplasty is performed bymaking incisions near the female breast 12, as shown at the dotted linesat 14, 15, 16. The augmentation mammaplasty operation can be performedusing a 21/2 inch inframammary incision, approximately 2 inches lateralto the midline running laterally to approximately 41/2" and some 5centimeters down from the infra-aerola line, following the infra-mammarycrease skin line. A pocket is formed beneath the breast, as shown inFIG. 4 and should be made adequately with a sharp and blunt dissectionover the fascia of the Pectoralis Major muscle and be large enough toadequately accommodate the desired size of implant in the properlocation for proper aesthetic results in the augmentation of the breast12. After a period of time, a natural tissue capsule will form aroundthis new cohesive cast gel implantable prosthesis and will remain softinsofar as there will not be any artifical envelopes involved in aforeign body reaction. The elimination of the artificial envelopeeliminates any need for manipulation or procedures such as open orclosed capsulotomies.

The implantation of the cohesive, cast gel implantable prosthesis of thepresent invention eliminates the problems inherent with the implantationof non-cohesive gels. The non-cohesive gels can migrate into surroundingtissue before a natural tissue capsule is formed to be encapsulated inbizarre places as granulomas. Since the gel was not maintained in thedesired position, in a uniform cohesive mass, it was not thereforeencapsulated by the natural tissue capsule in one area.

Thus, there has been disclosed a unique way to solve the problem andeliminate the enclosed or open capsulotomy procedures which destroy oralter the natural tissue capsule, while eliminating the problem of theoffending foreign body. This unique way induces implantation proceduresas normally done, but also the use of a cohesive, soft, cast gelimplantable prosthesis thereby eliminating the body struggle between twoor more envelopes fighting each other and producing contracture. Anatural tissue capsule will then be formed around the inert, cast gelimplantable prosthesis without allowing its migration into surroundingtissue because of its cohesiveness. The implant will therefore remainsoft and in proper position giving the result of a natural feeling anatural looking female breast.

The subject implant also aides in the management of caranoma of thebreast with emphasis on breast conservation. For example, many patientselect implanted radioisotope therapy as an alternative to a modifiedradical mastectomy. This therapy includes the use of long sharp hollowneedles, which are inserted into the breast. Thin, flexible plastictubing containing radioisotopes is inserted through each needle. Whenthe radioisotope is properly positioned adjacent to cancerous tissue,the needles are withdrawn, leaving the tubing in the breast for theduration of the therapy.

Conventionally, extreme precautions have been taken to avoid puncturingthe prosthesis during the radioisotope therapy. If puncture occurs, thetherapy must be immediately interrupted, the patient prepared forsurgery, the prosthesis removed, and the area previously holding theprosthesis cleaned. In many cases, one can not tell if puncture hasoccurred, but the patient exhibits physiological signs indicative ofrupture, necessitating a surgical procedure that is sometimesunnecessary.

In other cases, women who have undergone modified radical mastectomieshave not been immediately fit with a prosthesis, owing to the likelihoodthat implanted radioisotope therapy would be required. The patientconsequently had to suffer the mental trauma of disfigurement until aprosthesis could be implanted.

The subject implant, however, is advantageous because the risk ofleakage is eliminated. Even if accidentally punctured by needles duringtherapy, the cohesive gel is non-leaking, and is highly likely toself-seal upon removal of the needle.

The method and structure of the prosthesis disclosed herein, of course,may be used for other types of implantation in other body areas. Inaddition, many modifications and variations of the invention arepossible in light of the above teachings. It is to be understood thatthe full scope of the invention is not limited to the details disclosedherein, but only by the claims and maybe practiced otherwise than asspecifically described.

I claim:
 1. An unconstrained cohesive gel prosthesis for implantation ina human body cavity normally substantially occupied by soft tissueconsisting essentially of:an unconstrained molded pressure-dispersingcohesive homogeneous gel elastomer formed to fit the shape and size of abody cavity normally substantially occupied by soft tissue in the humanbody, the cohesion of said gel being such that it can be stretchedsubstantially more than 21% of its length without the appearance ofstress cracks in the gel, the gel being sufficiently cross linked sothat the gel has a non-flowing characteristic.
 2. A method for avoidingpost-surgical contracture of breast implants comprising the stepsoffilling a cavity normally occupied by breast tissue with anunconstrained molded pressure-dispersing cohesvie gel elastomer implantsized and shaped to fit the cavity, the gel being sufficiently cohesiveso that it can be stretched substantially more than 21% of its lengthwithout the appearance of stress cracks in the gel, and beingsufficiently cross linked to exhibit a non-flowing characteristic.